Hard magnetic disk drives (also known as fixed disk drives, rigid disk drives, and Winchester drives) are popularly used in conjunction with computers to store digital information. In the field of manufacturing hard magnetic disk drives various subassemblies are typically assembled first from individual components. These subassemblies are then integrated together and set within a housing to form the completed disk drive system. One such subassembly which is critical to disk drive operations is known as the head gimbal assembly (HGA).
The HGA is typically comprised of an actuator, flexures, magnetic transducers (also known as "heads"), sliders, and a coil. The actuator has a plurality of arms extending outwards. Mounted at the end of each arm is a flexure to which a head is affixed. The head is used to write bits of information onto a circular magnetic disk which magnetically stores the information. Later, the head can retrieve or read the stored information from the disk.
Sliders straddle the head so that the head can "fly" across the top of the circular magnetic disk. Multiple disks are stacked on top of one another in order to increase the storage capacity. When an electrical current is applied to the coil, the HGA moves the heads radially across the stack of circular magnetic disks with each head accessing one disk. An electrical motor rotates the stack of disks about a spindle. By moving the heads radially across the disks as the disks are rotated, data can be written onto and read off the disks as a series of bits arranged in concentric "tracks".
In manufacturing the HGA's, the magnetic wires which are electrically coupled at one end to the heads need to have their other ends soldered onto a flex circuit. These magnetic wires are used to conduct electrical signals between the heads and a flex circuit. A flex circuit is a thin, flexible length of plastic embedded with conductors. Since the HGA is pivoted quite frequently (in order to position the heads over the desired portion of the disk), electrical wires would eventually break due to fatigue. Hence, a flex circuit is used to electrically couple the heads to the rest of the disk drive system. Thereby, a computer can send appropriate electrical signals instruction the hard disk drive to store certain digital data. The disk drive system passes the digital data via the flex circuit through the magnetic wire to the head which then writes the digital data onto the magnetic disk.
Similarly, a computer can instruct the hard disk drive to retrieve the stored data. The disk drive command the HGA to position the appropriate head over the portion of the disk containing the desired data. The head then reads the magnetic data off the disk and converts it into an electrical signal. The electrical signal is sent to the rest of the disk drive system via the magnetic wires and the flex circuit. The disk drive system processes the electrical signal (e.g., amplified, filtered, perhaps decompressed, etc.) and then sends it to the computer.
The magnetic wires can be manually soldered onto the flex circuit. However, a faster, more efficient method is to use a reflow soldering technique. First, the HGA is placed in the reflow solder fixture to firmly hold it in place during the reflow soldering process. In reflow soldering, the solder pads of the flex circuit are first prepared with solder. The fixture is moved so that a solder pad is positioned under the reflow solder tip. The corresponding magnetic wire is then pulled over the solder pad. The tip is then lowered onto the magnetic wire and solder pad. The tip is heated so that it burns off the insulation on the magnetic wire and melts the solder. Thereby, the magnetic wire is soldered onto the solder pad of the flex circuit. The operator pulls off any excess wire by means of tweezers. This process is repeated for each magnetic wire. For forty megabyte hard disk drives, typically six magnetic wires must be soldered. For eighty megabyte hard disk drives, typically twelve magnetic wires must be soldered.
After the magnetic wires are soldered onto the flex circuit, the assembled HGA is removed from the reflow solder fixture. A plastic head protector is often placed over the heads. The head protector acts as a safeguard against damages from handling. Each assembled HGA is then placed on carrying containers. The carrying containers are transported down to a static test station. The head protector is removed, and the assembled HGA is subjected to electrical tests which tests certain electrical performances of the HGA to verify that it is working properly.
However, there are numerous problems associated with this prior art manufacturing process. One major disadvantage is that because the HGA is extremely delicate, especially the heads and the magnetic wires, it is highly susceptible to being damaged each time it is handled. In the prior art manufacturing process, the HGA is handled quite frequently (i.e., the HGA must be inserted into and removed from the reflow solder station, the head protector is fitted onto and detached from the HGA, the HGA is placed onto and removed from the carrying tray, and the HGA is inserted onto and removed from the static test station).
Another disadvantage is that as the carrying containers are queued to the static test station, a Work In Progress (WIP) buildup results. In other words, there is no immediate feedback on what was just performed. The feedback is delayed. This adds to the complexity of tracking the overall manufacturing cycle.
Yet another problem is that, typically, the person who operates the reflow solder station is not the same person who operates the static test station. Hence, the operator of the reflow solder station does not know whether he or she is performing the soldering correctly. For example, if the operator mistakenly believes that a particular wire is to be soldered to a particular solder pad or otherwise incorrectly performs the soldering procedure, the operator is likely to repeat the error because there is no immediate feedback informing the operator of the error.
Still another disadvantage with the prior art is that it is inefficient. If the static test station detects an error attributable to incorrect soldering, the HGA must then be removed from the static test fixture, the head protector must be refitted over the heads. It must then be carried back to the reflow solder station. Operation of the reflow solder station must be halted so that the failed HGA may be substituted. The head protector must be removed, and the failed HGA is inserted into the reflow solder fixtured and "touched up." Then, the "touched up" HGA is removed from the reflow solder fixture. The head protector is refitted. The HGA is carried back to the static test station. The head protector is removed, and the HGA is reinserted back in the static test fixture. The HGA is again subjected to the electrical performance tests to make sure that the "touch ups" fixed the problem. If the HGA fails the tests, the procedure described above must be repeated. Thus, the prior art manufacturing process is inefficient and results in wasted time and effort.
What is needed then is an assembly station which integrates both the reflow soldering and testing operations for a more simple, efficient manufacturing process.